title: Precise alignment of peptidyl tRNA by the decoding center is essential for EF-G-dependent translocation.
abstract: Translocation is an essential step in the elongation cycle of the protein synthesis that allows for the continual incorporation of new amino acids to the growing polypeptide. Movement of mRNA and tRNAs within the ribosome is catalyzed by EF-G binding and GTP hydrolysis. The 30S subunit decoding center is crucial for the selection of the cognate tRNA. However, it is not clear whether the decoding center participates in translocation. We disrupted the interactions in the decoding center by mutating the universally conserved 16S rRNA bases G530, A1492, and A1493, and the effects of these mutations on translocation were studied. Our results show that point mutation of any of these 16S rRNA bases inhibits EF-G-dependent translocation. Furthermore, the mutant ribosomes showed increased puromycin reactivity in the pretranslocation complexes, indicating that the dynamic equilibrium of the peptidyl tRNA between the classical and hybrid-state configurations is influenced by contacts in the decoding center.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0314, USA.
authors.forename: Lucia
authors.initials: L
authors.lastname: Garcia-Ortega
authors.forename: Jenise
authors.initials: J
authors.lastname: Stephen
authors.forename: Simpson
authors.initials: S
authors.lastname: Joseph
mesh_terms: D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D016297:Mutagenesis, Site-Directed; D010441:Peptide Chain Elongation, Translational / Q000187:drug effects / Q000502:physiology*; D020653:Peptide Elongation Factor G / Q000378:metabolism*; D017354:Point Mutation; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D012343:RNA, Transfer / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D054680:Ribosome Subunits, Small, Bacterial / Q000502:physiology; D012270:Ribosomes / Q000187:drug effects / Q000502:physiology; D013033:Sparsomycin / Q000494:pharmacology; D013050:Spectrometry, Fluorescence
chemical_list: D020653:Peptide Elongation Factor G; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D012346:RNA, Transfer, Amino Acyl; C019037:tRNA, peptidyl-; D013033:Sparsomycin; D006160:Guanosine Triphosphate; D012343:RNA, Transfer